Basterfield and Aston. — The Chemistry of Rimu-resin. 485 

 Calculated. 



R,0 = 27-7 

 Ba = 15-1 



Silver Salt — CigHigOg, Ag. — An amorphous llocculent pre- 

 cipitate prepared from a solution of the barium salt. 



Calculated. Found. 



Ag = 29-4 ... ... 29-0 and 29-7 



Benzoyl Bimuic Acid. — This compound was prepared by 

 shaking the alkaline solution of rimuic acid with excess of 

 benzoyl-chloride. It is sparingly soluble in cold alcohol ; from 

 hot alcoholic solutions it separates on rapid cooling as a 

 transparent jelly, which becomes crystalline on standing. 



Calculated for 

 CisHigO, CeHsCO, CO.H. Found. 



C = 75-8 ... ... ... 75 6 



H= 6-6 ... ... ... 6-6 



Kimuic acid boils at 296°-300° at 21 mm. By continued 

 heating at 300° it loses water, and is converted into a colour- 

 less compound which is no longer soluble in alkalis, ether, or 

 the usual organic solvents, and cannot be distilled without de- 

 composition. Eimuic acid does not yield an ethereal salt 

 when treated with absolute alcohol and hydrochloric-acid gas. 

 It readily forms two crystalline nitro-acids and a sulphonic 

 acid, which will be described in a later paper. 



It is of interest to note that Podocarpus cupressimcm, a 

 tree occurring in Java, contains as the chief constituent of its 

 heart-resin an acid (podocarpic acid) which is so similar to 

 rimuic acid that the two compounds might readily be mistaken 

 for one another. Upon comparison it becomes clear that the 

 two acids belong to the same homologous series — CnH,,j_gOH, 



CO2H. 



Rimuic Acid, Podocarpic Acid, 



C16H.20O3. C17H22O3. 



M.P. 192-193° C. ... 186-188° C. 



[a] J, -150° ... +136° 



The acids differ in the number of molecules of water with 

 which their salts crystallize. The following points of resem- 

 blance are remarkable : Both yield sparingly soluble acid 

 ammonium salts which crystallize with one molecule of 

 water. Both yield anhydrides when heated to 300° C. Both 

 yield crystalline mono and dinitro derivatives the acid salts 

 of which are yellow, the normal salts scarlet or crimson. 

 The dinitro derivatives are peculiarly sensitive to the action 

 •of light. Both acids, again, dissolve readily in cold con- 

 centrated sulphuric acid, and yield sulphonic acids the 

 barium salts of which are sparingly soluble and highly 



